javascript - 测试JavaScript中是否未定义某些内容(Test if something is not undefined in JavaScript)

Question

I'm checking if(response[0].title !== undefined) , but I get the error:

(我正在检查if(response[0].title !== undefined) ，但是我得到了错误：)

Uncaught TypeError: Cannot read property 'title' of undefined.

(未捕获的TypeError：无法读取未定义的属性“title”。)

  ask by Raimonds translate from so

Answer 1

response[0] is not defined, check if it is defined and then check for its property title.

(未定义response[0] ，检查是否已定义，然后检查其属性标题。)

if(typeof response[0] !== 'undefined' && typeof response[0].title !== 'undefined'){
    //Do something
}